Anti-retroviral activity of 2',3'-dideoxy-3'-fluoronucleosides

Abstract

Use of a compound of the formula ##STR1## wherein Base is thymine, Cytosine, adenine or guanine, or a physiologically acceptable salt thereof, for therapeutic treatment of hepatitis B virus infections and to a method for such treatment.

Description

This application is a continuation of application Ser. No. 07/603,215 filed on Oct. 25, 1990, now abandoned, which is a Divisional of Ser. No. 07/319,840 filed Mar. 7, 1989, which is a Continuation of Ser. No. 07/143,577 filed Dec. 30, 1987, now abandoned.

FIELD OF THE INVENTION

The present invention relates to the use of known chemical compounds and physiologically acceptable salts thereof for the therapeutic treatment of the Acquired Immuno Deficiency Syndrome (AIDS), infections by Human Immunodeficiency Virus, hepatitis B virus infections and retrovirus infections for such control and treatment in animals and man.

BACKGROUND OF THE INVENTION

In the late seventies a new disease was reported, which subsequently was referred to as Acquired Immuno Deficiency Syndrome (AIDS). It is now generally accepted that a retrovirus referred to as HIV (Human Immuno Deficiency Virus, formerly known as Human T-cell Lymphotropic Virus (HTLV-III) or Lymphadenopathy Associated Virus (LAV) plays an essential role in the etiology of AIDS.

AIDS is characterized by a profound immunodeficiency due to low numbers of lymphocyte-T-helper cells, which are the targets for HIV (also called HTLV-III/LAV) infection. The profound immunodeficiency in AIDS patients makes these patients highly susceptible to a variety of opportunistic infections of bacterial, fungal, protozoal or viral etiology. The etiological agents among viral opportunistic infections are often found in the herpes virus group, i.e., Herpes simplex virus (HSV), Varicella Zoster virus (VZV), Epstein-Barr virus (EBV) and, especially, cytomegalovirus (CMV). Other retroviruses affecting humans are HTLV-I and II and examples of retroviruses affecting animals are feline leukemia virus and equine infectious anaemia virus.

Hepatitis B virus infections cause severe disease such as acute hepatitis, chronic hepatitis, fulminant hepatitis in a considerable number of persons. It is estimated that there are 200 million patients with chronic hepatitis B infection in the world. A considerable number of the chronic cases progress to liver cirrosis and liver tumours. In some cases the hepatitis infections also take a rapid and severe course as in fulminant B hepatitis with about 90% mortality. At present there is no known effective treatment against hepatitis B infections.

PRIOR ART

The compound 3'-deoxy-3'-fluoro-thymidine is described in Journal f. prakt. Chemie, Vol. 315, 895-900 (1973) as having cytostatic and virustatic activity as selective inhibitor of DNA synthesis. In the same article the synthesis of the compound 2',3'-dideoxy-3'-fluorocytidine is described.

The compounds 2',3'-dideoxy-3'-fluoroadenosine and 2',3'-dideoxy-3'-fluoroguanosine are described in the East-German patents DD 158903 and DD 209197, respectively, as virostatic agents.

DISCLOSURE OF THE INVENTION

It has been found according to the present invention that the compounds of the formula ##STR2## wherein Base is thenine, cytosine, adenine or guanine, or a physiologically acceptable salt thereof, present a new possibility to block the multiplication of hepatitis B virus, by use of a nucleoside analogue of said formula. Accordingly, the nucleoside analogue of said formula and physiologically acceptable salts thereof, have beneficial properties as therapeutic agents in the treatment of hepatitis B virus infections, respectively.

Hepatitis B virus (HBV) is a DNA virus with a unique circular double-stranded DNA genome which is partly single-stranded. It contains a specific DNA polymerase required for vital replication. This DNA polymerase also acts as a reverse transcriptase during the replication of HBV DNA via an RNA intermediate.

The compounds of the invention are transformed by cells/or enzymes to triphosphates which inhibit the activity of DNA polymerase of hepatitis B virus.

The following known compounds constitute part of the invention as therapeutic agents in treatment of hepatitis B virus infections: ##STR3##

3'-Deoxy-3'-fluorothymidine is especially preferred as an agent for treatment of hepatitis B virus infections in animal and man.

In clinical practice the nucleosides of the invention will normally be administered orally, by injection or by infusion in the form of a pharmaceutical preparation comprising the active ingredient in the form of the original compound or optionally in the form of a pharmaceutically acceptable salt thereof, in association with a pharmaceutically acceptable carrier which may be a solid, semi-solid or liquid diluent or an ingestible capsule. The compound may also be used without carrier material. As examples of pharmaceutical preparations may be mentioned tablets, dragees, capsules, granulates, suspensions, elixirs, syrups, solutions etc. Usually the active substance will comprise between 0.05 and 20% for preparations intended for injection and between 10 and 90% for preparations intended for oral administration.

In the treatment of patients suffering from hepatitis B virus infections, it will be preferred to administer the compounds by any suitable route including the oral, parenteral, rectal, nasal, topical and vaginal route. The parenteral route includes subcutaneous, intramuscular, intravenous and sublingual administration. The topical route includes buccal and sublingual administration. The dosage at which the active ingredients ape administered may vary within a wide range and will depend on various factors such as the severity of the infection, the age of patient etc., and may have to be individually adjusted. As a possible range for the amount of the compounds of the invention or a physiologically acceptable salt thereof be administered per day may be mentioned from about 10 mg to about 10 000 mg, preferentially 100-500 mg for intravenous administration and preferentially 100-1000 mg for oral administration.

SALTS

The physiologically acceptable salts of the nucleosides of the invention are suitable acid addition salts, derived from non-toxic acids. Such acid addition salts include, for example, those derived from inorganic acids such as hydrochloric acid, hydroiodic acid, sulphuric acid, phosphoric acid and sulfamic acid, organic sulphonic acids such as p-toluenesulphonic acid, methanesulphonic acid, p-chlorobenzonesulphonic acid, ethanesulfonic acid, and benzensulfonic acid and organic carboxylic acids such as maleic acid, malic acid, lactic acid, citric acid, tartaric acid, succinic acid, oxalic acid, acetic acid, isethionic acid, gluconic acid, pantothenic acid and lactobionic acid.

EXPERIMENTAL TESTS

PAC Test I. Effect of 3'-deoxy-3'-fluorothymidine as a triphosphate on the DNA polymerase of hepatitis B virus (HBV) in cell free assay

Since hepatitis B virus cannot be grown in cell cultures, a cell-free assay system of the hepatitis B virus DNA polymerase has been used to investigate the effect of 3'-deoxy-3'-fluorothymidine. 3'-Deoxy-3'-fluorothymidine in cells is transformed to 3'-deoxy- 3'-fluorothymidine- 5'-triphosphate.

The HBV associated DNA polymerase activity can be measured in vitro (Kaplan et al., J. Virol., 12,995-1005, 1973). A slight modification of this method has been used to test the substance for inhibition of this DNA polymerase activity. (Nordenfelt E., (Oberg, B., Helgstrand E. and Miller E. Acta path., Microbiol. Scand. Sect B, 88:169-175, 1980). With this assay the 3'-deoxy-3'-fluorothymidine-5'-triphosphate has been tested, instead of the prodrug 3'-deoxy- 3'-fluorothymidine, to evaluate its potential against hepatitis B virus DNA polymerase.

3'-deoxy-3'-fluorothymidine-5'-triphosphate was added to the final concentrations of 0.01 μM, 0.05 μM, 0.1 μM, 0.5 μM and 1.0 μM in the reaction mixture. The inhibition is calculated after 3 hours incubation at 37°C and based on cpm compared to control with added water. The test result is shown in Table I.

TABLE I
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Inhibition of hepatitis B virus (HBV) DNA polymerase activity
by 3'-deoxy-3'-fluorothymidine-5'-triphosphate
Concentration of
3'-deoxy-3'-fluorothymidine-
5'-triphosphate (μM)
% inhibition
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0.01               17
0.05               17
0.1                39
0.5                79
1                  88
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From the results shown in Table I the apparent ID₅0 -value of 3'-deoxy-3'-fluorothymidine was found to be 0.16 μM.

Test II. Effect of 3'-deoxy-3'-fluorothymidine as a triphosphate on the reverse transcriptase of HIV (HTLV-III/LAV) in cell free assay.

A cell-free assay system has been used to investigate the inhibition of 3'-deoxy-3'-fluorothymidine on reverse transcriptase of HIV (HTLV-III/LAV). The assay was performed as described by Vrang et Oberg, Antimicrob. Agents Chemother. 29,867-872 (1986). With this assay the 3'-deoxy-3'-fluoro-thymidine-5'-triphosphate has been tested, instead of the prodrug 3'-deoxy-3'-fluorothymidine to evaluate its potential against reverse transcriptase from HIV (HTLV-III/LAV). The test result is shown in Table II.

TABLE II
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Inhibition of HIV (HTLV-III/LAV) reverse transcriptase by
3'-deoxy-3'-fluorothymidine-5'-triphosphate
Concentration of 5'-triphosphate
3'-deoxy-3'-fluorothymidine (μM)
% inhibition
______________________________________
0.01                 12
0.05                 27
0.1                  38
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From the results in Table II, the ID₅0 -value of 3'-deoxy-3'-fluoro-thymidine with regard to the activity of HIV reverse transcriptase was found to be 0.2 μM by extrapolation.

Test III. Effect of 3'-deoxy-3'-fluorothymidine on HIV (HTLV-III/LAV) in H9 cells

PAC MATERIAL AND METHODS; HIV INFECTION OF H9 CELLS

H9-cells (2×1O⁶) were preincubated overnight with 3'-deoxy-3'-fluorothymidine at various concentrations. The cells were then pelleted and dispersed in 2.5 ml phosphate buffered saline (PBS) including 2 μg/ml Polybrene. After incubation for 30 min the cells were pelleted and infected with HIV. After an adsorption period of 1 hour the cells were pelleted and washed once with 2.5 ml PBS. To each culture 7 ml media including 3'-deoxy-3'-fluorothymidine at studied concentrations was added. Samples for reverse transcriptase activity tests were taken as indicated.

ASSAY

1.3 ml samples from the supernatant of each culture were centrifuged at 18 000 rpm in a 55-34 rotor for 1.5 hours and the virus pellet resuspended in 100 μl buffer containing 50 mM Tris-HC1, pH 7.5; 35 mM KC1; 4 mM DTT; 1 mM EDTA; 1.3 % Triton X-100.50 μl samples were taken to the reverse transcriptase activity tests and analyzed in a 100 μl reaction mixture containing 75 mM Tris-HC1, pH 8.0; 60 mM KC1; 6.2 mM MgC1₂ ; 6 mM DTT; 0.5 mM EDTA; 0.65 % Triton X-100; 100 μg/ml BSA; 25 μCi/ml ³ H-dTTP (spec activity 80 Ci/mmol); 2.5 μg/ml (dT)₁2-18 ; and 2.0 μg/ml (rA)_n. Incubation was for 1 hour at 37°C and the TCA-insoluble product precipitated onto Whatman GF/A filter papers, washed and dried, and counted in a liquid scintillation counter. The test result is shown in Table III.

The amounts of reverse transcriptase molecules and their total activity expressed in HIV-infected cell cultures is correlated to the amount of HIV particles present. The addition of an effective antiviral agent which inhibits the production of new HIV particles, also decreases the amount of reverse transcriptase molecules and is expressed as a decreased total activity.

TABLE III
______________________________________
Effect of 3'-
deoxy-3'-fluorothymidine on the expressed reverse transcriptase
activity in HIV (HTLV-III/LAV)-infected H9 cells.
Reverse transcriptase activity (cpm × 10-3) in the
presence of indicated amounts (μM) of 3'-deoxy-3'-
Days
fluorothymidine
post-infection
0        0.01    0.05  0.1   0.5  1.0
______________________________________
4       0.9      0.5     0.3   0.2   0.3  0.3
8       19       1.3     0.3   0.2   0.3  0.2
11       17       1.9     0.4   0.5   0.5  0.5
15       11       2.7     0.6   0.4   0.3  0.4
18       27       28      0.5   0.4   0.6  0.5
22       46       52      1.6   0.2   0.1  0.1
29       16       21      3.1   0.2   0.2  0.2
______________________________________

In Table III is shown the effects of different concentrations of 3'-deoxy-3'-fluorothymidine on the reverse transcriptase activity of HIV (HTLV-III/LAV) during an incubation period of several weeks. The presence of 3'-deoxy-3'-fluorothymidine at 0.1 μM and higher concentrations completely prevents the enzyme activity during at least 29 days. At 0.05 μM of 3'-deoxy-3'-fluorothymidine no significant enzyme activity was detected up to 22 days and at 0.01 μM concentration, enzyme activity was not detected up to 11 days.

Claims

1. A method for therapeutic treatment of hepatitis B virus (HBV) infections in man, comprising administering to a patient in need thereof, an effective anti-hepatitis B viral amount of a compound of the formula ##STR4## wherein Base is selected from the group consisting of thymine, cytosine, adenine and guanine, or a physiologically acceptable salt thereof.

2. The method of claim 1, wherein said compound is 3'-deoxy-3'-fluorothymidine or a physiologically acceptable salt thereof.

3. The method according to claim 1, wherein said compound is 3'-deoxy-3'-fluoroguanosine.